The following points will be examined during the next year. 1. The effect of prior priming with virus on the capacity of T cells to recognize H-2 different virus-infected cells. This will be done using both adult thymectomized and non-thymectomized individuals. 2. The effect of prior priming with alloantigen on the capacity to recognize virus presented in the context of that alloantigen. Possible cross-reactions between the alloantigen and virus plus self T cell repertoires. 4. The effect of administration of monoclonal antibodies specific for a particular viral determinant on the mobilizations of T cells specific for that virus in the thoracic duct lymph. 5. The use of negative selection protocols to examine the interaction between high responder and low responder T cells in the virus-immune response.